Building air distribution systems require stable and accurately controllable air valve or air dampers for control of building heating and air circulation functions. For maximum efficiency, large numbers of such air dampers are usually computer controlled simultaneously in order to provided the proper heat and air distribution within the building. Air dampers have been disclosed having longitudinal blades provided with sealing gaskets with the blades arranged in a venetian blind arrangement. Such systems are prone to leakage due to alignment problems which can arise over time. Other damper systems employ linkage assemblies having relatively slow response times.
Yet other systems employ piston driven damper plates utilizing a pair of guide pins which slide in an open ended slot and a guide pin slidably mounted in a closed longitudinal guideway wherein in the fully closed position pins are located at the closed ends of the guideway and slot. Systems of this type are disclosed in U.S. Pat. No. 4,605,198 issued Aug. 12, 1986 to Seal-Air Control Systems Inc. A drawback to this kind of arrangement is that backlash problems developing in the damper plate opening and closing mechanism over time will cause the seal formed by the damper plate compressed against a gasket to degrade resulting in leakage. When this damper is opened, the guide pins move translationally along the slots thereby translationally displacing the damper plate until the pin in the open ended slot pivots around the pin located at the end portion of the closed guideway whereupon the damper plate rotates from a vertical to substantially horizontal position. A drawback to this type of movement is that it is very difficult to reproducibly control the motion of the damper plate as it rotates open. Furthermore, it is very difficult to control the position of the damper plate in order to modulate the flow of air through the duct when the plate is not in the fully open or fully closed position. In other words, with this arrangement, there is not a desired linear relationship between the amount of piston movement and the amount of air flow through the system.
It is an object of the present invention to provide an air damper mechanism which permits the same degree of control over a damper throughout its entire movement between the open and closed position.